Films or Surfaces Including Positional Tracking Marks

ABSTRACT

Various implementations of the invention comprise a surface or film having a plurality of three-dimensional structures embodied on or within the surface or film, each of the three-dimensional structures having a reflecting surface configured to retro-reflect radiation from a radiation source back to a detector located at the radiation source.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Application is a continuation application is U.S. application Ser.No. 15/206,197, filed on Jul. 8, 2016, entitled “Films or SurfacesIncluding Positional Tracking Marks,” now U.S. Pat. No. ______; which inturn claims priority to U.S. Provisional Patent Application No.62/190,592, filed on Jul. 9, 2015, and entitled “Films includingPositional Tracking Marks.” Each of the foregoing applications isincorporated herein by reference.

FIELD OF THE INVENTION

The invention is generally related to films and/or surfaces that includeretro-reflective, uniquely defined positional tracking marks and moreparticularly, to using such films and/or surfaces as a human/digitalinterface.

BACKGROUND OF THE INVENTION

Digital-human interfaces (e.g., user interfaces) that provide closer toreal life experiences are desired as digital devices evolve. Writing anddrawing with human hands are fundamental processes for experience andexpression. Existing devices that use touch sensitive screens are notprecise enough to reproduce such experience or expression withsufficient accuracy. For example, a typical line width of a pen orpencil is 0.5 mm, and no screen technology available today sufficientlyreproduces the handwriting experience at a reasonable cost. Somecommercially available digitizing systems utilize position-dependenttwo-dimensional dots that are detected by sensor in a pen such as thatavailable from Anoto Group AB.

Devices such as capacitive or resistive touch screens provide both input(touch) and output (display) capabilities. A touch screen is formed byplacing a transparent overlay proximate to the display surface. Suchoverlays typically detect input (i.e., a “touch”) based upon a change inelectrical properties of the overlay. The accuracy and resolution ofthese overlays is typically insufficient for precision writing, drawing,marking, etc., to provide a rewarding user experience. Existing systemsthat do provide the expected level of accuracy and resolution in touch(hand or writing instrument) frequently require unacceptably highbackground in the visual perception.

Other existing devices utilize a pen that includes a radiation sourceand a camera, to be used on visual devices such as display or screen forhuman-digital interface. These pens rely on tiny ink dots on the surfaceof the display. These ink dots, which are not transparent, block lightfrom the underlying display and in effect, degrade the intensity of thedisplay. Other existing devices rely on photo luminescent marks disposedon a surface; however, the intensity of fluorescence is not sufficientfor a practical device. Other existing devices that use reflection(specular reflection) are not useful for handwriting applicationsbecause the angle of incidence needs to be nearly the same as the angleof reflection for the pen to detect the marks.

SUMMARY OF THE INVENTION

Various implementations of the invention comprise a surface or film thatincludes retro-reflective, uniquely defined positional tracking marksuseful in connection with a human/digital interface. In someimplementations of the invention, the surface or film includesthree-dimensional structures (referred to herein as “marks”) embodiedonto or into the surface or films that are detectable by electronicdevices in invisible portions of the electromagnetic spectrum. In someimplementations of the invention, the surface or film selectivelyreflects a portion of the electromagnetic spectrum. In someimplementations of the invention, the film is transparent (orsubstantially transparent) to visible portions of the electromagneticspectrum. In some implementations of the invention, the film iscomprised of multiple layers.

In various implementations of the invention, the surface or film, andthe marks embodied therein, is comprised of extremely durable materials.In various implementations of the invention, neither the surface/film,nor the marks embodied therein, visually impair digital display screensor other surfaces on which the films may be overlaid.

According to various implementations of the invention, these surfaces orfilms provide invisible tracking and digitization of informationgenerated through motion of a stylus on screens and protective surfaces.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a forearm-hand (palm) angle of a human hand accordingto various implementations of the invention.

FIG. 2 illustrates a cone of vision of a human viewer according tovarious implementations of the invention.

FIG. 3 illustrates a ray diagram of specular reflection for a commonreflective surface.

FIG. 4 illustrates a surface or film that selectively reflects aparticular band of wavelengths of radiation, while allowing for passageof other wavelengths or radiation, according to various implementationsof the invention.

FIG. 5A illustrates three-dimensional structures of a surface or filmretro-reflecting radiation from sources according to variousimplementations of the invention.

FIG. 5B illustrates three-dimensional structures of a surface or filmselectively retro-reflecting one band of radiation from sources, whiletransmitting other bands of radiation according to variousimplementations of the invention.

FIG. 6A illustrates three-dimensional structures having a hemisphericalshape according to various implementations of the invention.

FIG. 6B illustrates three-dimensional structures having a partiallyspherical shape according to various implementations of the invention.

FIG. 6C illustrates three-dimensional structures having a conical shapeaccording to various implementations of the invention.

FIG. 6D illustrates three-dimensional structures having an oblong domeshape according to various implementations of the invention.

FIG. 7 illustrates a digital reading device which may be used withvarious implementations of the invention.

FIG. 8A illustrates an example of a film patterned with threedimensional structures illuminated by light in the visual spectrum inaccordance with various implementations of the invention.

FIG. 8B illustrates the example of the film patterned with threedimensional structures illuminated by light at 850 nm in accordance withvarious implementations of the invention.

DETAILED DESCRIPTION

The various implementations of the invention may be understood morereadily by reference to the following description in connection with theaccompanying figures and examples, which form a part of this disclosure.This invention is not limited to the specific devices, methods,applications, conditions or parameters described and/or shown herein,and the terminology used herein is for the purpose of describingparticular implementations by way of example only and is not intended tobe limiting of the claimed invention. In addition, as used in thespecification including the claims, the singular forms “a,” “an,” and“the” include the plural, and reference to a particular numerical valueincludes at least that particular value, unless the context clearlydictates otherwise. The term “plurality”, as used herein, means morethan one. When a range of values is expressed, another implementationincludes from the one particular value and/or to the other particularvalue. Similarly, when values are expressed as approximations, by use ofthe antecedent “about,” it will be understood that the particular valueforms another implementation. All ranges are inclusive and combinable.

Various implementations of the invention are now described in thecontext of a film that may be overlaid onto another surface (e.g., asurface of a computer display, a surface of a mobile device display, asurface of another display, and/or other surfaces). However, theinvention is not limited to such films, but includes surfaces moregenerally. For example, the three-dimensional structures (i.e., marks)described herein may be incorporated directly onto or into a surfaceitself (i.e., without a film with such structures overlaid onto thesurface). So while various implementations of the invention aredescribed as films, such implementations apply equally to surfacesthemselves as would be appreciated.

Various implementations of the invention comprise a transparent filmwith various marks embodied therein that are configured to interact witha pen or stylus having a radiation source (e.g., light) and a detector.According to various implementations of the invention, the marksembodied in the film reflect radiation back to its source (e.g., a penor other writing stylus) when used at a typical handwriting angle of30°-60° (i.e., an acute angle formed between the pen and the writingsurface). Such marks are said to “retro-reflect” radiation back to thesource of the radiation, that is, so that the path of the reflectedradiation is substantially parallel to, though in the opposite directionof, the path of the incident radiation. More particularly, the markcomprises a three-dimensional structure embodied in or on the film, anda surface of such three-dimensional structure retro-reflects at least aselected band of radiation back to its source. Conventional printedmarks generally used in conventional reading are not considered threedimensional because the height or thickness of such marks issubstantially less than the dimension in width or length (e.g., thesmallest dimension of such printed marks is less that 15% of the otherdimensions of the mark). According to various implementations of theinvention, the smallest dimension of a three dimensional mark is atleast 20% of the other two dimensions of the mark. For purposes of thisdescription, a “retro-reflector” refers to a surface that reflectsradiation so that at least a portion of rays from a source and incidentto the surface (i.e., “incident rays”) are reflected back as reflectedrays along a similar path toward the source. In other words, theincident rays and the reflected rays are substantially parallel to oneanother though in opposite directions. In some implementations of theinvention, a surface is a retro-reflector if its reflected rays arereflected back within +/−15° from the incident rays.

Various implementations of the invention comprise a visually transparentfilm that can be “retro-fitted” on existing displays or other surfaces(e.g., notebooks, walls, white boards, tabletops, etc.) to provide anappropriate digital-human interface. In various implementations, thefilm may also function as a protective shield.

Various implementations of the invention comprise a film that istransparent to the visible spectrum (e.g., 380 nm to 700 nm) in theviewing angle of +/−75° to +/−110° to the normal defining the plane ofthe film. In some implementations of the invention, the film isreflective only to 405+/−10 nm band of radiation; and transmits the restof the 380 nm-700 nm Band of radiation.

Various implementations of the invention comprise a film that includesretro-reflective marks responsive to a pen having a light source atpen-to-surface (acute) angles of 30° to 60° (sometimes referred toherein as a handwriting angle) consistent with a forearm-hand (palm)angle of a human hand as illustrated in FIG. 1. In some of suchimplementations of the invention, such marks are transparent in thevisible spectrum within the cone of vision of a human viewer, and asdefined by ISO 13406-02, and as illustrated in FIG. 2, illustrated as asolid angle defined by the viewer eye and corners a,b,c,d of viewingframe.

Various implementations of the invention comprise a film includingthree-dimensional marks embodied therein, where the marks may be in theform of domes, spheres (or portions thereof), paraboloids, dimples,cones, or dents or other forms in various dimensions and shapes suchthat a surface of the marks retro-reflect at least a selected band ofincident radiation at various handwriting angles.

FIG. 3 illustrates a ray diagram of specular reflection for a commonreflective surface 300 such as aluminum foil or a mirror, where an angleof incidence, θ_(i), is equal to an angle of reflection, θ_(r), at allthree wavelengths λ₁, λ₂, and λ₃. (For purposes of clarity, FIG. 3specifically illustrates the angles only for λ₂.)

FIG. 4 illustrates a film 400 that selectively reflects a particularband of wavelengths of radiation, while allowing for passage of (i.e.,being transparent to) the other wavelengths or radiation, according tovarious implementations of the invention. More particularly, film 400reflects radiation at wavelength λ₁, while film 400 is transparent toradiation at wavelengths λ₂ and λ₃. In some implementations of theinvention, film 400 may be a multilayer film.

FIG. 5A illustrates an example of three-dimensional structures 510(e.g., marks) of a film 500 retro-reflecting radiation from sources 520due to a particular geometry of the three-dimensional structuresaccording to various implementations of the invention. In case of thesegeometries, at least a portion of the reflected radiation issubstantially parallel to the incident radiation, especially within therange of the angles of pen-to-surface interaction (i.e., handwritingangles). As illustrated, at least a selected band of incident radiation(e.g., all three wavelengths λ₁, λ₂, and λ₃) is reflected back to itsrespective source 520 along a same path (illustrated in FIG. 5A as asource 520-1 for wavelength λ₁, a source 520-2 for wavelength λ₂, and asource 520-3 for wavelength λ₃).

FIG. 5B illustrates an example of the three-dimensional structures of amultilayered film 550 selectively retro-reflecting one band ofradiation, while transmitting other bands of radiation, due to aparticular geometry of the three-dimensional structures 510 andcomposition of film 550, according to various implementations of theinvention. As illustrated, the incident light at wavelength λ₁ isretro-reflected (i.e., reflected back) to its source 520-1, whereas film550 is transparent (i.e., little or no reflection) to radiation atwavelengths λ₂ or λ₃.

FIGS. 6A-6D illustrate various examples of three-dimensional structures610 (e.g., marks) that may be used by various implementations of theinvention. In some implementations of the invention, various shapes ofstructures 610 may be used to tailor the angle of apparentretro-reflection of radiation incident at various angles according tovarious implementations of the invention. According to variousimplementations of the invention, structures 610 reflect at least aselected band of incident light back in the general direction of source(not illustrated in FIGS. 6A-6D) of the light. In some implementationsof the invention, the various shapes of structures 610 may be dictatedbased on manufacturing techniques or processes tolerated by films 600themselves. In some implementations of the invention, three-dimensionalstructures 610 may be embodied on a surface of film 600. In someimplementations of the invention, three-dimensional structures 610 maybe formed as voids or hollowed-structures within film 600. In someimplementations of the invention, three-dimensional structures 610 maybe formed upwardly as illustrated in FIGS. 6A-6D (and elsewhere). Insome implementations of the invention, three-dimensional structures 610may be formed downwardly as would be appreciated. In someimplementations of the invention, three-dimensional structures 610 maybe formed from multilayered films. In some implementations of theinvention, the wavelength selection may be due to multilayered film. Insome implementations of the invention, the wavelength selection may bedue to nano-structures in the film.

FIGS. 6A-6D illustrate cross sections of various three-dimensionalstructures 610 that may be embodied on or in films 600 of variousimplementations of the invention. FIG. 6A illustrates three-dimensionalstructures 610A (i.e., marks) as domes having a hemispherical shapeaccording to various implementations of the invention. In suchimplementations, the marks are hemispherical, having a radius, R, as adistance between the highest point of the mark from the plane, whichcorresponds to one half of a diameter, D, of the dome; and where thetangent to the dome at the point of intersection with the plane (i.e.,angle of the tangent) is 90°. In some implementations of the invention,the diameter, D, of the dome may be between 50 to 300 microns; in someimplementations of the invention, the diameter, D, may be between 60 to200 microns; in some implementations of the invention, the diameter, D,may be between 70 to 150 microns; and in some implementations of theinvention, other diameters may be used as would be appreciated.

FIG. 6B illustrates three-dimensional structures 610B (i.e., marks) as ¼to <½ domes having a partially rounded or partially spherically shapedaccording to various implementations of the invention. In suchimplementations, the marks are partially spherical, having a height, H,as a distance between the highest point of the mark from the plane,which roughly corresponds to one-third or one-quarter of a base, B; andthe tangent to the surface at the point of intersection with the plane(i.e., acute angle of the tangent) is between 45° and 60°. In someimplementations of the invention, the diameter of the base, B, of thedome may be between 50 to 300 microns; in some implementations of theinvention, the diameter of the base, B, of the dome may be between 60 to200 microns; in some implementations of the invention, the diameter ofthe base, B, of the dome may be between 70 to 150 microns; and in someimplementations of the invention, other diameters of the base, B, may beused as would be appreciated.

FIG. 6C illustrates three-dimensional structures 610C (i.e., marks)having a conical shape according to various implementations of theinvention. In such implementations, the marks may comprise a cone havinga height, H, that is one-half to one-fourth of a measure of a base, B,(i.e., diameter of the base) of the cone. In some implementations of theinvention, an angle of the sides of the cone relative to the plane(i.e., acute angle of the side) may be between 45° and 60°. In someimplementations of the invention, the diameter of the base, B, of thecone may be between 50 to 300 microns; in some implementations of theinvention, the diameter of the base, B, of the dome may be between 60 to200 microns; in some implementations of the invention, the diameter ofthe base, B, of the cone may be between 70 to 150 microns; and in someimplementations of the invention, other diameters of the base, B, may beused as would be appreciated.

FIG. 6D illustrates three-dimensional structures 610D (i.e., marks)having an oblong dome shape having a ratio of a vertical diameter, DV,to a horizontal diameter, DH, of between 3:1 to 1.1:1 according tovarious implementations of the invention. In such implementations, themarks are egg-shaped, appearing as parabolas in cross-section. In someimplementations of the invention, the base (acute) angle of the eggwalls with the plane is between 45° and 60°. In some implementations ofthe invention, the horizontal diameter of the egg is between 50 to 300microns; in some implementations of the invention, the horizontaldiameter of the egg is between 60 to 200 microns; and in someimplementations of the invention, the horizontal diameter of the egg isbetween 70 to 150 microns.

In some implementations of the invention, the wavelength selectionreferred to herein may be accomplished using a multilayered film. Insome implementations of of invention, the three dimensional marks areformed in multilayered films that may be selectively reflective in405+/−10 nm or NIR bands, and have high transmission in rest of thevisible band. In some implementations of of invention, the threedimensional marks are formed in multilayered films that may beselectively reflective in 850+/−10 nm or NIR bands, and have hightransmission in visible band. Wavelength selective reflectors, whichinclude multilayer interference films, alternate a layer of materialhaving a high index of refraction with a layer of material having a lowindex of refraction, as would be appreciated. In reflectors of thistype, each layer has a thickness of one-quarter of the wavelength of apredetermined color of light; the low index layers tend to reducereflection of wavelengths selected for transmission by the film, whilethe high index layers increase reflection of desired wave bands by thefilm. Such reflectors, as a whole, provide wavelength selectivecharacteristics by transmitting a substantial proportion of light of onewaveband, while reflecting a. substantial proportion of light of anotherwaveband. For example U.S. Pat. No. 5,233,465, which is incorporatedherein by reference describes films made from polymer layers selectivein reflectance and transmittance to selected wavebands. Commerciallyavailable multilayered films which may be used in variousimplementations of this invention include Crystalline 90, available from3M Corporation, St. Paul, Minn., USA. Other films that utilizenano-structures including silver nano-particles may also be used aswould be appreciated.

Various implementations of the invention combine the wavelengthselectivity of the multilayer materials with the retro-reflectorgeometry of the three dimensional structures to create marks transparentto visible wave bands, while being reflective to NIR or 405+/−10 nm waveband.

Various implementations of the invention provide for digital tracking(i.e., identification of the marks embodied within the film) withoutinterfering with human vision. As such, in some implementations of theinvention, any of the films described above may comprise a multilayerfilm that may be, for example, reflective in the near infrared spectrumand transparent in the visible spectrum. Various LED light sources emitradiation in the 780 nm to 900 nm (i.e., near infrared “NIR” range) or280 nm to 550 nm (UV/VIS) LED. Such LED light sources may be detected byphotosensitive cameras equipped with near infrared band pass filters tofilter all light, except for the light from an NIR LED source. In someimplementations of the invention, the NIR LED source emits radiation inthe 850 nm+/−15 nm wave band. In some implementations of the invention,the UV/VIS LED source emits radiation in the 405 nm+/−10 nm wave band.

According to various implementations of the invention, the films and thethree-dimensional structures therein may be prepared by a variety oftechniques. Some implementations of the invention employ multilayerfilms that are transparent to the visible spectrum, but reflect NIRradiation. Such films, which are widely available from 3M,Dupont-Tenjin, Llamar, etc., are used as home and automobile windowtreatments to filter sunlight. According to various implementations ofthe invention, the three-dimensional structures may be micro-imprintedor embossed in these films.

Some implementations of the invention employ multilayered IR reflectivefilms, commercially available from a variety of sources to create marksthat may selectively reflect wavelengths in accordance with variousimplementations of the invention.

In some implementations of the invention, the three-dimensionalstructures may be created via deposition of the film material(s) onto asubstrate having the desired geometry as would be appreciated. In someimplementations of the invention, the three-dimensional structures maybe created by etching such structures having the desired geometry out ofthe film material(s) as would be appreciated. In some implementations ofthe invention, the three-dimensional structures may be created via athree-dimensional printer that prints such structures onto a surface. Insome implementations of the invention, pre-prepared multi-layeredmicrospheres (or other relevant geometry) may be deposited on thesurfaces, pre-printed with an adhesive in the mark areas, followed byfurther curing to permanently attach the microspheres to the surface. Insome implementations of the invention, the three-dimensional structuresmay be embossed or punched into the film material(s) as would beappreciated.

In some implementations of the invention, the marks may be created onmaterials such as plastic or glass surfaces for display applications. Inimplementations of the invention not requiring transparent films such aswhite board, or writing pads, the marks may be created in films such asaluminum foil, which is neutral to human vision.

In some implementations of the invention, the patterns for the marks maybe in any digitally formatted pattern, such those commonly referred toas Anoto patterns, and available from Anoto, Inc., of Westborough, Mass.Such patterns enable a stylus or pen to determine a precise location ofthe tip of the stylus or pen on the paper or screen as would beappreciated. Other patterns may be utilized as would be appreciated.

In some implementations of the invention, a digital reading device fordetecting and digitizing the marks comprises a stylus or a pen, such asAnotoPen, also available from Anoto, Inc., which is held at theforearm-hand (palm) angle while in human use. Such pens have a radiationsource (e.g., light source) and a camera positioned inside in a mannersuch that the light reflected from the marks may be sensed by the cameraat typical handwriting angles and be digitally recorded by the pen orstylus in communication with an electronic device such as a computer,tablet, phone, and a PDA.

In some implementations of the invention, a digital reading device, orpen, 700, such as that illustrated in FIG. 7, includes of a cylindricalhollow body 705 configured for good writing grip. In someimplementations of the invention, pen 700 has a removable blunt endpointer, or stylus, 710 configured to imitate writing action. In someimplementations of the invention, pen 700 is equipped with an LED fightsource 720 that emits an incident ray 722 having a wavelength outsidethe human visible range and configured to produce reflections from themarks as a reflected ray 724. In some implementations of the invention,pen 700 is also equipped with a sensor 730 to receive and detectreflected ray 724 and produce an electronic signal. LED light source 720and sensor 730 are positioned to direct light to and receive fight fromwriting surface 750, and three-dimensional structures 755 therein(illustrated, but not limited to “domes”) in accordance with variousimplementations of the invention. In some implementations of theinvention the structures 755 are multilayered films. In someimplementations of the invention, LED light source 720 and sensor 730transmit and receive the light of desired wavelength through a filterwindow 740. Sensor 730 is configured to detect retro-reflected ray 724while being small enough to be integrated in pen 700. In someimplementations of the invention, an angle between incident ray 722 andreflected ray 724 may be 15° or less, though other angles may beaccommodated as would be appreciated. In some implementations of theinvention, the electronic signal from sensor 730 is fed in to a digitalprocessing unit 760 that is in wired or wireless communication withdigital communication unit 770, which in turn is in communication withan electronic device such as a computer. PDA, phone, kindle,e-inkreader, i-pad, or other electronic device (not otherwise illustrated inFIG. 7) as would be appreciated.

In various implementations of the invention, the films and marks thereinare a ‘stand alone’ surface for the tracking and detecting the humaninteraction with the film. According to various implementations of theinvention, the films may be integrated with surfaces associated with adigital device. For example, the film of the invention may be affixed orotherwise overlaid onto a digital LED or LCD display of a computer orhand-held device including mobile devices. Also for example, the film ofthe invention may also serve as a protective shield for the digital LEDor LCD display in a manner similar to those shields provided withvarious protective covers manufactured by, for example, Otter Box, etc.Also for example, the film of the invention may be attached over a whiteboard or note pad. Also for example, the film of the invention may beintegrated with a heads-up-display, for example, of an airplane,automobile, etc. Also for example, the film of the invention may beincluded in laptop privacy screens, which are attached over the displayscreens. Also for example, the film of the invention may be attachedover e-Reader devices, such as Kindle, etc., and used for tracking andmarking customized text highlights, etc.

In some implementations of the invention, an operation of reading a markcomprises: 1) sending light pulses towards marks on the film; 2) recordretro-reflected light pulses reflected from various marks on the film;3) record the retro-reflected pulses, their locations based on themarks, and their time; and 4) track the respective positions and motionof the pen based on the retro-reflected pulses.

Example—A 3″×2″ piece of commercial automotive film from 3M, referred toas CR-90, with VLT >88% and NIR reflectance of >80%, was mounted on ahard board with paper cups. A One Touch Delica 33 gauge (0.02096 micron)lancet manufactured by LifeScan, Inc. Milpitas, Calif., was used tocreate deformations (e.g., marks) in the film by applying enoughpressure to cause an indentation, but not penetrate the film. Theindentation pattern was of the inventor's name (“MAK”) and observed formthe opposite side. The domes thus created in the patterned film wereobserved through digital microscope with visual light at about an angleof 45°, and then with digital microscope equipped with a visual lightcutoff filter and an 850 nm light source. The visual light did not showany perceptible visible interference with the background, while the 850nm photographs showed clear bright pattern. FIG. 8A illustrates apatterned film 800 illuminated with light in the visual spectrum; whileFIG. 8B illustrates the patterned film 800 illuminated with light at 850nm.

1-20. (canceled)
 21. A film comprising: a wavelength selective film,wherein the wavelength selective film is reflective for infrared ornear-infrared radiation and transparent for visible radiation, whereinthe wavelength selective film forms a plurality of three-dimensionalstructures embodied on or within the wavelength selective film, each ofthe plurality of three-dimensional structures having a reflectingsurface configured to retro-reflect infrared or near-infrared radiationfrom a radiation source back to a detector located at the radiationsource, wherein an angle between the radiation from the radiation sourceincident to the reflecting surface and radiation reflected from thereflecting surface is between +/−15 degrees.
 22. The film of claim 21,wherein each of the plurality of three-dimensional structures comprisesa hemispherical or partially hemispherical structure.
 23. The film ofclaim 21, wherein each of the plurality of three-dimensional structurescomprises a conical structure.
 24. The film of claim 21, wherein each ofthe plurality of three-dimensional structures comprises a parabolicstructure.
 25. The film of claim 21, wherein the wavelength selectivefilm comprises a reflective mufti-layered film forming the reflectivesurface of each of the plurality of three-dimensional structures. 26.The film of claim 21, wherein the plurality of three-dimensionalstructures are embossed into the wavelength selective film.
 27. The filmof claim 21, wherein the plurality of three-dimensional structures areformed in a digital tracking pattern configured to provide a preciselocation within the pattern.
 28. A surface comprising: a wavelengthselective material reflective for infrared or near-infrared radiationand transparent for visible radiation, the wavelength selective materialforming a plurality of three-dimensional structures embodied on orwithin the surface, each of the plurality of three-dimensionalstructures having a reflecting surface configured to retro-reflectinfrared or near-infrared radiation from a radiation source back to adetector located at the radiation source.
 29. The surface of claim 28,further comprising an electronic display.
 30. The surface of claim 29,wherein a writing surface is incorporated into a viewing surface of thedisplay.
 31. The surface of claim 28, wherein each of the plurality ofthree-dimensional structures comprises a hemispherical structure, apartial hemispherical structure, a conical structure or a parabolicstructure.
 32. The surface of claim 28, wherein the plurality ofthree-dimensional structures are embossed into the wavelength selectivematerial.
 33. The surface of claim 28, wherein the plurality ofthree-dimensional structures are formed in a digital tracking patternconfigured to provide a precise location within the pattern.
 34. Anarticle of manufacture comprising: a protective cover configured tosubstantially cover a handheld electronic device, wherein the electronicdevice includes an integral display, the protective cover having anopening configured to permit viewing of the integral display; and awavelength selective film configured to be disposed in the opening ofthe protective cover and adjacent to the integral display of theelectronic device, wherein the wavelength selective film is transparentfor visible radiation emitted from the integral display, the wavelengthselective film forming a plurality of a three-dimensional structuresembodied on or within the wavelength selective film, each of theplurality of three-dimensional structures having a surface configured toretro-reflect infrared or near-infrared radiation from a radiationsource back to a detector located at the radiation source.
 35. Thearticle of manufacture of claim 34, wherein each of the plurality ofthree-dimensional structures comprises a hemispherical structure, apartially hemispherical structure, a parabolic structure, or a conicalstructure.
 36. The article of manufacture of claim 34, wherein theplurality of three-dimensional structures are formed from and embossedinto the wavelength selective film.
 37. The article of manufacture ofclaim 34, wherein the plurality of three-dimensional structures areformed in a digital tracking pattern configured to provide a preciselocation within the pattern.